Transcription by RNA polymerase II in animal requires both specific transcription factors such as Ap-1, Sp-1 and basal transcription factors such as TFIID and RNA polymerase II. Previously I isolated human CCG1 gene with a temperature-sensitive mutant cells, tsBN462, which could not enter the S phase at high temperature, 39.5 degreesC and is a mutant of a transcription factor, TAF250. The TFIID complex which contains CCG1 lies between specific transcription factors and other basal transcription factor and this may modulate transcription like gear in a car. I will study how CCG1/TAF250 works in accepting signals from specific transcription factors and in transmitting various signals to other basal transcription factors, mainly focusing on complex formation of the TFIID complex during the cell cycle and the effect of phosphorylation of CCG1 to transcription. I will construct hamster cell lines containing HA- tagged CCG1 and TBP to analyze complex of TFIID. I will determine the phosphorylation sites of CCG1 and introduce mutations to these sites to see the significance of these sites to transcription. I will identify protein kinases that phosphorylate CCG1 to study the significance of phosphorylation in signal transduction. Since tsBN462 cells show apoptosis at a nonpermissive temperature, CCG1 may have some critical roles in apoptosis. In order to understand roles of CCG1 on apoptosis and cancer, I will study interaction of CCG1 with recessive oncogene p53 and oncogene c-myc, which are both transcription factors.